# Electricity: Circuits and their Components

## Overview

This chapter introduces students to the basics of electricity, exploring how circuits work, what their components are, and how electricity powers various everyday devices. Through simple activities and observations, students learn about electric cells, batteries, lamps, LEDs, switches, circuit diagrams, conductors, and insulators. Safety precautions related to electricity are also emphasized.

## Key Topics Covered

### 1. Uses of Electricity

* Electricity is essential in daily life and used across:

* **Entertainment**: Television, radio
* **Communication**: Mobile phones, internet
* **Lighting**: Homes, offices, streets
* **Cooking**: Toasters, ovens, microwaves
* **Transportation**: Trains, buses, lifts
* **Heating and Cooling**: Heaters, geysers, ACs
* **Others**: Computers, water pumps, cranes

* Students are encouraged to explore additional uses and new ways of classifying them.

### 2. Introduction to Safe Use of Electricity

* Electricity can be dangerous if misused.
* Safe experiments should use only dry cells or batteries.
* Power supply from sockets should never be used in school experiments.

### 3. Understanding the Torchlight

* A torchlight contains a lamp, switch, and batteries (cells).
* The switch completes or breaks the circuit inside the torch.
* When the switch is on, the electric current flows and lights the lamp.

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### 4. Components of a Simple Electric Circuit

#### A. Electric Cell

* Has two terminals: **positive (+)** and **negative (–)**
* Small protruding cap = positive terminal
* Flat metal base = negative terminal

#### B. Battery

* A combination of two or more cells
* Cells must be connected: **positive to negative**
* Provides more power and duration

#### C. Electric Lamp (Incandescent)

* Contains a **filament**: a thin wire that glows when current flows through it
* Filament is supported by thicker wires inside a glass bulb
* Lamp glows only when circuit is complete

#### D. LED (Light Emitting Diode)

* More common in modern torches
* Has two terminals:

* **Longer wire** = positive
* **Shorter wire** = negative
* LED glows only if connected correctly (current flows one way)

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### 5. Constructing a Simple Circuit

* **Materials Needed**: Electric cell, lamp/LED, cell holder, lamp holder, connecting wires
* **Steps**:

* Attach wires to holders or directly using electrical tape
* Connect cell terminals to lamp terminals
* The lamp glows only if the circuit is complete

#### Key Observation:

* A circuit must be a **closed loop** for electricity to flow and make the lamp glow.

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### 6. Electrical Circuit

* A **circuit** is a complete path for current to flow.
* Current flows from the **positive terminal to the negative terminal** of a cell.
* In incandescent lamps, the direction of connection doesn’t matter, but for **LEDs**, correct polarity is essential.

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### 7. Electric Switch

* A **switch** is a device that opens or closes a circuit.
* In the **ON** position: current flows, lamp glows
* In the **OFF** position: the path is broken, no current flows

#### Activity:

* Make a simple switch using drawing pins, a paper clip, cardboard, and wires.

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### 8. Circuit Diagrams and Symbols

* Electrical components can be represented using standard symbols.
* Helps in easy understanding and communication across the world.

#### Common Symbols:

| Component | Symbol Description |
| --------------- | --------------------------- |
| Electric Cell | One long and one short line |
| Battery | Series of cells |
| Lamp | Circle with a cross |
| LED | Triangle with arrows |
| Switch (ON/OFF) | Gaps with dots and lines |
| Wire | Straight line |

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### 9. Conductors and Insulators

* **Conductors**: Materials that allow electricity to flow (e.g., metals like copper, aluminium)
* **Insulators**: Materials that do not allow current to pass (e.g., plastic, rubber, glass)
* **Why wires are coated**: To protect users from electric shocks using insulating materials

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### 10. Types of Electricity

* **DC (Direct Current)**: Comes from cells or batteries, flows in one direction
* **AC (Alternating Current)**: Comes from wall sockets, used for larger appliances

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## New Terms and Simple Definitions

| Term | Definition |
| --------------- | ------------------------------------------------------------- |
| Electric cell | A small portable source of electricity |
| Terminal | The end of a cell or device that connects in a circuit |
| Battery | Two or more cells connected together |
| Filament | Thin wire in a lamp that glows when current flows |
| LED | A light source that works on low power and specific direction |
| Switch | A device that opens or closes a circuit |
| Circuit | A closed path for electric current to flow |
| Conductor | Material that allows electricity to pass |
| Insulator | Material that does not allow electricity to pass |
| Circuit diagram | A drawing using symbols to show a circuit |


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## Practice Questions

### Easy (3 Questions)

1. **What are the two terminals of an electric cell called?**
**Answer**: Positive and Negative terminals
**Explanation**: One end is marked with a '+' (positive), the other with a '–' (negative).

2. **What part of an electric lamp glows?**
**Answer**: The filament
**Explanation**: The thin wire inside the bulb heats up and produces light.

3. **What material is commonly used to make electric wires?**
**Answer**: Copper
**Explanation**: It is a good conductor and easily available.

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### Medium (2 Questions)

4. **Why does an LED not glow when connected in reverse?**
**Answer**: Because current flows through an LED in only one direction.
**Explanation**: The longer wire (positive) must connect to the positive terminal of the battery.

5. **What is the role of a switch in an electric circuit?**
**Answer**: It opens or closes the circuit.
**Explanation**: In the ON position, the switch completes the path for current; in the OFF position, it breaks it.

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### Difficult (3 Questions)

6. **How is a battery different from an electric cell?**
**Answer**: A battery is a combination of two or more electric cells.
**Explanation**: It provides more energy or runs the device for longer.

7. **In a circuit with an incandescent lamp and a battery, what will happen if the filament breaks?**
**Answer**: The lamp will not glow.
**Explanation**: A broken filament stops the current flow.

8. **Why are electrical wires coated with plastic or rubber?**
**Answer**: To prevent electric shock.
**Explanation**: These are insulators that stop current from escaping the wire.

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### Very Difficult (2 Questions)

9. **You are given a circuit with a cell, an LED, and a switch. The LED is not glowing. List at least 3 possible reasons.**
**Answer**:

* LED is connected in reverse
* Cell is not working
* Switch is in OFF position or circuit is incomplete
**Explanation**: All these can break the circuit or prevent current from flowing properly.

10. **Design an activity to identify which among six given cells are working.**
**Answer**:

* **Items needed**: Lamp, two wires, a holder
* **Procedure**: Connect each cell one-by-one to the lamp through wires. If lamp glows, cell is working.
**Explanation**: Working cells complete the circuit and allow current to flow.

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